I experienced the same at ULN with MIAT two years ago, also in July. I recalled that airport elevation and hot weather further complicates the strong wind issues. For Air China and Air Busan's flight, since they are originating from Beijing and Busan, they just simply don't depart from home hub until they have good visibility on the weather. But for MIAT, they just want to depart ASAP if weather permits, so they make all pax getting ready at airport.